Leeds Astronomical Society LAS Meetings Observing Membership

 

 

M66 - Group

(Ivor Trueman)
(M66)
(M65)
(NGC3628 - Hamburger Galaxy)
(James Clark)

Information...

The M66 Group, aka the 'Leo Triplet' is a small group of galaxies approx. 35 million light years away in the constellation of Leo.

It's thought that M66 (lower left hand side of image) owes it's distorted shape to the gravitational pull from M65 (lower right hand side of image). M66 is also know to have an unusual distribution of atomic & molecular hydrogen, with the atomic hydrogen present in the outer regions & concentrations of molecular hydrogen nearer the galaxy core.

NGC3628 (top middle of image) which is nicknamed the 'Hamburger' galaxy, is seen edge-on with a conspicuous dust band across the middle and an 'X' shaped bulge at the centre. The latter indicates that the galaxy probably has a central 'bar' feature.

For more info. see the Wikipedia entries for Leo Triplet, M65; M66 and NGC3628.

 

×

Map

×

Measuring Angles

Hold your arm at full length, then close one eye & use the hand shapes shown above to measure the angular distance between the stars.

(Ain't anatomy wonderful!)

×

Apparent Magnitude

The apparent magnitude of a star is a measure of how bright it appears from Earth. The scale was introduced over 2,000 years ago by the Greek astronomer Hipparchus, who grouped stars into six categories. The brightest 20 or so were deemed to be 'first magnitude', slightly dimmer stars 'second magnitude', and so on until the barely visible stars were classed as 'sixth magnitude'.

Later it was recognised that our eyesight, once it has been given time to get used to darkness, has a logarithmic response. i.e. a Mag. 1 star is actually 2.512 times brighter than a Mag. 2 star, or 6.310 times brighter than a Mag. 3 star (2.512 x 2.512 = 6.310).

The six Magnitudes thus corresponds to a 2.5126 difference in brightness or 100x.

Apparent magnitude

Today the scale has now been extended, so that brighter objects can have an apparent magnitude of 0 or even negative. The brightest star Sirius, for example, has an apparent magnitude of -1.44 and the Sun is a whopping -26.74, due to it's close proximity to Earth.